Electrostatic field sensor and security system in interior and exterior spaces

ABSTRACT

Electrostatic field sensor and security system in interior spaces and exterior spaces which can measure electrostatic fields and the variations thereof along a metal conductor that acts as a detection probe or antenna ( 1 ). The antenna ( 1 ) is connected to an electronic circuit ( 2, 3, 4, 31, 32 ) which is able to decode the changes in the electrostatic field around the conductor and to detect minuscule variations in the electrostatic field by means of a processor ( 7 ) enabling the clear detection of a human presence in an area surrounding the antenna ( 1 ) and the ability to differentiate between a human presence and any other type of animal or object.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application for Patent is a Divisional of U.S. patent applicationSer. No. 14/888,346, titled “ELECTROSTATIC FIELD SENSOR AND SECURITYSYSTEM IN INTERIOR AND EXTERIOR SPACES”, filed on Oct. 30, 2015, whichis a 35 U.S.C. § 371 National Phase of International Application No.PCT/ES2014/070719, filed Sep. 23, 2014, which claims priority to SpanishPatent Application No. P201331388, filed Sep. 24, 2013. The disclosuresof these applications are incorporated in their entireties herein byreference.

OBJECT OF THE INVENTION

The object of the invention is a sensor capable of measuringelectrostatic fields and a security system for homes. The invention hasits practical application in the security sector, and more specificallyin private or domestic security in properties, its main aim being anintrusion detection through a door, window, or fence, although it can beused in other locations such as walls or partition walls.

STATE OF THE ART

Currently, in the field of private security for indoor spaces, differenttypes of devices capable of detecting an intrusion into a home orsimilar are used. Among the different types of detection devices are thefollowing:

-   -   (a) Volumetric sensors, which detect changes in the volume of        the measuring area and translate them into motion detection.    -   (b) Door-opening sensors that detect when a door or window is        opened or closed.    -   (c) Infrared barrier sensors that detect the passage of an        object between their transmitters and receivers    -   (d) ibration or glass break sensor that detect vibration in        crystals when they are beaten or suffer a break

All these devices have in common that are installed inside a house.Therefore, they do not offer a preventive security, since they are onlycapable of detecting an intrusion when this has already happened.Therefore, it is not a preventive security system, but an event warningor alarm system. On the other hand, both volumetric sensors and infraredbarrier sensors are unable to, in addition, discriminate the types ofmoving objects or the different movements that occur within its range.

To avoid these problems, the best solution is the electrostatic fieldsensors. However, most of the documents are based on uncontrolledsignals and on the indirect measure of capacity depending on thevariation in the resonance frequency of the signal and/or in itsimpedance.

For example, the document ES 2152335 T3 describes a detector deviceconnected to an antenna for detecting small capacitive changes in anelectric or electromagnetic field around the antenna, said devicecomprising: generating means for generating an electric orelectromagnetic field around said antenna; balancing means formaintaining the generated electric or electromagnetic field around saidantenna in a balanced condition; filtering means for preventing thedetector device from being affected by changes in the temperature andhumidity; detection means for detecting small changes in the generatedelectric or electromagnetic field around said antenna; and indicatingmeans for indicating that a change in the electric or electromagneticfield has occurred; and characterized in that the generating means are asquare wave generator, preferably generating a square wave between 50 Hzand 5000 Hz, and in that the unaffected square wave from said generatorand the square wave capacitively affected by the field surrounding theantenna are fed to amplifier means to amplify the difference thereof.

Thanks to this detector device, it is achieved a security system in afirst presence area indicating that the intruder has approached theprotected object at a distance of between 100 and 150 cm; a secondpresence area which indicates that the intruder has approached theobject protected at a distance of 30 cm; and a third presence area whichindicates that the intruder almost makes contact with the protectedobject.

Therefore, this invention creates a square wave, wherein depending onthe variation of the frequency of the same the related capacity can becalculated. This signal creates a magnetic field in the conductor whichis out of control, i.e., its field lines extend in all directions and,in addition, undergoes variations with the temperature, humidity andother conditions, so it needs to correct these problems.

DESCRIPTION OF THE INVENTION

The object of this invention is a sensor capable of measuringdisturbances occurring in the electrostatic field around a probe thatacts as an electrode or antenna, due to the human presence in itsvicinity. This electrostatic field is also redirected in a controlledmanner to focus their influence on a certain area. In addition, thesensor is able to differentiate on the basis of the magnitude of thechange, persons from other living beings or material objects.

In turn, this sensor is an integral part of a security system designedfor preventive detection of an intrusion into a delimited space, throughthe integration of sensors, wireless communication devices and centralalarm management.

More specifically, in a first aspect of the invention, the electrostaticfield sensor is characterized in that it comprises two electrostaticfield-measuring circuits, signals of which are decoupled with respect toeach other by a decoupling circuit; and wherein said electrostaticfield-measuring circuits are connected with an antenna consisting of acoaxial cable through a phase-measuring circuit.

In a second practical embodiment of the invention, the electrostatic andmagnetic field sensor that is characterized by the use of a tunercircuit with operating frequency less than 5 MHz. The parts in which theelectronic circuit is divided would be: RLC tank circuit andphase-stabilizing circuit. It has a coaxial cable connected to saidcircuit to act as an antenna and generate the propagation of theelectrostatic field. Said antenna can be of several layers of electrodein order to control the zone of influence of fields generated.

In a second aspect of the invention, the security system for interiorand exterior spaces comprises at least one electrostatic field sensor asdescribed above connected to a signal conditioner circuit and aprocessor comprising a memory that incorporates at least a software withinstructions configured to detect the variations in the electrostaticfield received from the sensor; determine the volume and density of theobject that has generated the variation in the electrostatic field; andestablish whether the volume and density of the object corresponds to anunauthorized intrusion and emit an encrypted signal to a switchboard.

Finally, in a third aspect of the invention is claimed the method fordetection of intruders in homes comprising the steps of: (a) detect thevariation in a electrostatic field with at least an electrostatic fieldsensor as described above; (b) determine the volume and density of theobject that has generated a variation in the electrostatic field; (c)establish whether said volume and density of the object corresponds toan unauthorized intrusion; and (d) emit an alarm encrypted signal.

The invention is based on the capacity of sensor object of the inventionto measure the variations in the electrostatic field existing around aconductor, in the case of the invention a coaxial cable, which acts as aprobe or antenna, when said field is affected by the influence of acharged body, such as the human body.

The human body, like any other existing object, has its own electricalcharacteristics, dependent on the materials, density, volume,temperature and conductivity. The differences in the potential betweenthe different objects result in electrostatic interactions from anobject to another when they come into contact or are close to eachother. This effect is used by the sensor object of the invention,achieving the continuous measurement of fluctuations that said fieldcauses in an electronic circuit connected to it. This circuit, throughthe changes in the field magnitude is able to distinguish differenttypes of bodies or objects and to discriminate the human presence fromanother material or animal presence.

Indeed, the sensor object of the invention, in carrying out thecontinuous measurement of the capacity, it molds the electrical fieldgenerated on the antenna and through infinite field lines, a processorconnected to the same allows determining the volume and density ofmaterial which generates the field fluctuation on the antenna.

The invention is applied to security systems in homes, giving thecapacity to detect intrusions proactively in doors, windows and fences,i.e. the detection capability before the intrusion takes place.

Throughout the description and claims, the word “comprises” and itsvariations are not intended to exclude other technical features,additives, components or steps. For those skilled in the art, otherobjects, advantages and characteristics of the invention will emerge inpart from the description and in part from the practice of theinvention. The following examples and drawings are provided by way ofillustration, and are not intended to be limiting of the presentinvention. Furthermore, the present invention covers all the possiblecombinations of particular and preferred embodiments herein indicated.

BRIEF DESCRIPTION OF THE FIGURES

There follows a very brief description of a series of drawings that helpto provide a better understanding of the invention and which areassociated expressly with an embodiment of said invention that ispresented as a non-limiting example thereof.

FIG. 1 shows a scheme of the electrostatic field sensor object of theinvention.

FIG. 2 shows a scheme of the security system object of the invention.

FIG. 3 shows a second embodiment of the electrostatic field sensorobject of the invention.

EXPLANATION OF A DETAILED EMBODIMENT OF THE INVENTION

As can be seen in FIG. 1, the electrostatic field sensor comprises anantenna 1 consisting of a coaxial cable, either with one, two or threewires. The antenna 1 is directly connected with a phase-measuringcircuit 2, which is a circuit that measures and analyzes the signals oftwo electrostatic field meters (3, 4) connected with the phase-measuringcircuit 2. The electrostatic field meters (3, 4) are decoupled from eachother by a decoupling circuit 5, so that the potential differencebetween both meters (3, 4) is zero, although the respective currents I₁and I₂ are different.

However, as shown in FIG. 3, the electrostatic field sensor object ofthe invention comprises a second practical embodiment, wherein theantenna 1 is connected to a tuner circuit with operating frequency lessthan 5 MHz comprising a RLC circuit 31 and a phase-stabilizing circuit32.

Like in the first embodiment, the antenna 1 is a coaxial cable connectedto said tuner circuit (31, 32) and also configured to generate thespread of the electric and magnetic field. This antenna may have amulti-layered electrode in order to control the zone of influence offields generated.

Since the antenna 1 is closed to the coaxial active, the magnetic fieldgenerated in the conductor is confined and therefore it is possible tocreate the field where desired, such as in a door, window or wall.

FIG. 2 shows a schematic view of the security system object of theinvention, comprising an electrostatic field sensor as described in theFIG. 1 or FIG. 3, connected with a signal conditioner circuit 6,essentially an analog-digital converter, which in turn is connected to aprocessor 7 configured to detect the variations in the electrostaticfield, establishing a kind of three-dimensional map with suchvariations, being able to determine the volume and density of the objectthat said variation has generated.

This processor 7, in turn, is connected to a radio frequency circuit 8which emits a signal encrypted towards a switchboard 9 which controlsthe entire installation.

In addition, the processor 7 is connected to a security camera 10 thatrecords the object detected and defined by the processor 7 as anunauthorized intrusion.

Finally, the processor 7 is connected with means of user identification11, preferably via Bluetooth®, in order to allow authorized system usersto have access to the site and do not generate an alarm signal.

The invention claimed is:
 1. A method for intrusion detection comprisingpropagation of an electric and magnetic field by one antenna and aroundthe one antenna, the one antenna connected to a tuner circuit with anoperating frequency less than 5 MHz; the tuner circuit consisting of aRLC circuit and a phase-stabilizing circuit; measuring variations in theelectric and magnetic field around the one antenna by the continuousdetection of fluctuations in said electric and magnetic field; moldingthe electric and magnetic filed generated around the one antenna bycarrying out continuous measurement of the variations in the electricand magnetic filed generated around the one antenna by which theelectric and magnetic field has been propagated; determining the volumeand density of an intrusion that has generated one of the variations inthe electric and magnetic filed around the one antenna; discriminating ahuman presence from another material or animal presence through thevolume and density of the intrusion; establishing if the human presenceis authorized or unauthorized; and emitting an encrypted signal to aswitchboard via a radio frequency emitter.
 2. The method of claim 1further comprising: recording an image of an unauthorized humanpresence.